The technology of lapping and polishing of optical components and other materials has existed for many hundreds of years and consists in its most simple and basic form of bringing the material to be lapped and/or polished into close physical contact with a flat plate loaded with fine abrasive either in a powder form or in a slurry, and moving in a repetitive pattern until sufficient material is removed from the workpiece to achieve the desired flatness and/or surface roughness. Many centuries have passed since the early era when optics for the first telescopes and microscopes were lapped and polished by hand by skilled craftsmen, however, the fundamental methods for lapping and polishing optical components, semiconductor and optoelectronic materials remain the same, with the principal difference that in contemporary times, automated lapping machines have largely replaced hand lapping and polishing methods and techniques.
Modern automated lapping and polishing machines invariably consist of a circular wheel or lapping plate fabricated from either cast iron or a composite material, rotating about its central axis powered by an electric motor. Either one or in some cases up to three or more workpiece holders are held in place near to the periphery of the rotating lapping plate by armature type assemblies that allow the workpiece holders to rotate about their own central axes while the large diameter lapping plate rotates beneath. The workpiece holder uses either vacuum or wax to secure the workpiece that is to be lapped and/or polished when in contact with the lapping plate. A slurry mix containing an abrasive such as diamond, alumina or boron carbide suspended in solution is dripped at a controlled rate onto the rotating lapping plate to effect material removal from the work piece(s). The lapping action is achieved through the simultaneous rotations of the workpiece holder and affixed workpiece about its own axis and the rotation of the large diameter lapping plate, in contact with the workpiece affixed to the holder. The contemporary automated approach to lapping and polishing provides many advantages over hand lapping including, much higher productivity, since the lapping machine can be operated continuously with minimal human intervention compared to hand lapping and polishing which requires continuous human exertion. There exist however, a number of significant drawbacks to the present techniques used in the automated apparatus for lapping and/or polishing. The principal drawback involves the very geometry and mechanics of the automated lapping apparatus which places the workpiece holders at the periphery of the lapping plate. Such placement of the workpieces, causes uneven wear of the plate after prolonged lapping and/or polishing with the apparatus. Conditioning of the lapping plate is then required to return it to a proper flatness, a process which is both time consuming and labor intensive and reduces the overall productivity of the machine.
A second further drawback of the existing automated lapping technology and apparatus includes the lapping plate materials which are predominantly either cast iron or copper composite. Cast iron is relatively soft and is capable of safely lapping a wide range of modern materials including those used in conventional optics such as glasses, as well as crystalline materials such as semiconductors and optoelectronic materials. Silicon and other semiconductor materials can be safely lapped with cast iron without risk of introducing impurities that can degrade the electronic properties of the semiconductors. Cast iron however, is intended for lapping only and cannot lap and polish a material simultaneously. Therefore, materials that are lapped directly on a cast iron plate must subsequently be polished using polishing pads woven most commonly from synthetic nylon or rayon fibers. Cast iron is prone to rusting and cannot be used over a prolonged time period with high purity water based abrasive slurries. This poses significant problems in terms of maintaining cleanliness for lapping sensitive semiconductor materials. In contrast to cast iron, the more recently developed copper composite lapping plates are useful for both the lapping and simultaneous polishing of materials which saves time and cost, in not having to polish a material after lapping using separate polishing pads. Unfortunately, the copper composite plates cannot be used for lapping and polishing silicon since the electronic properties of silicon are severely degraded by copper atom impurity in the silicon, unless the silicon material is used exclusively in optical rather than optoelectronic applications.
The ideal automated lapping machine will therefore combine the important characteristics of having a lapping plate fabricated from a corrosion resistant material that will support the use of clean, high purity water based abrasive slurries appropriate for lapping the full range optical glasses, semiconductors and optoelectronic materials while simultaneously polishing them. In addition, the lapping plate material must not contaminate any semiconductor workpieces that are meant to be lapped and polished. The method of lapping and polishing implemented by the apparatus on the workpieces should abrade the lapping plate uniformly on its entire surface, as to prevent non-uniform wear that requires time consuming and labor intensive, periodic conditioning or reflattening of the lapping plate.
An alternative method that allows for simultaneously lapping and polishing of the full range of optical materials including crystalline semiconductors and other optoelectronic materials in a clean manner using high purity water based abrasive slurries, and without a need to condition or reflatten the lapping plate, is described by the present invention. The present invention introduces a method for constructing an automated apparatus to perform simultaneous lapping and polishing of the full range of optical and optoelectronic materials using high purity water based abrasive slurry, without having to recondition the lapping plate. The lapping and polishing apparatus of the present invention can be implemented by using corrosion resistant stainless steel or nickel material for the lapping plate together with a synthetic nylon or rayon polishing pad affixed to said stainless steel or nickel plate. The workpiece holder uses vacuum to retain the workpiece. The primary lapping action is achieved in the apparatus by a linear, reciprocal, back and forth translation of the workpiece holder with affixed workpiece diametrically across the nylon or rayon pad, rigidly supported by the stainless steel or nickel lapping plate, which is loaded with a clean, high purity water based abrasive slurry. The linear movement of the workpiece and holder traces a straight line path across the center of the circular lapping plate. A secondary motion occurs in the apparatus as the workpiece holder with affixed workpiece, is rotated intermittently in step increments, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, thereby ensuring that the workpiece is lapped uniformly against the nylon or rayon pad supported by the stainless steel or nickel lapping plate. The stainless steel or nickel lapping plate is also rotated about its own axis to ensure that any wear on the nylon or rayon pad and stainless steel or nickel plate is uniform over the full area. The rotation of the stainless steel or nickel lapping plate however, is much slower than the frequency or rate of the linear, reciprocal back and forth translation of the workpiece holder, as such rotation of the lapping plate serves only to ensure uniform wear of the plate and nylon or rayon pad rather than actual abrading or material removal from the workpiece.
In summary, the manifold advantages of the method and apparatus of the present invention for lapping optical, semiconductor and optoelectronic materials include the capability of simultaneously lapping and polishing such materials while maintaining a high level of cleanliness and purity provided by water based abrasive slurries needed for semiconductor materials, at the same time wearing the stainless steel or nickel lapping plate and synthetic nylon or rayon pad uniformly, thereby obviating any need for time consuming and labor intensive conditioning or reflattening of the stainless steel or nickel lapping plate resulting from non-uniform wear. In many regards, the apparatus of the present invention automates the mechanical motion of the workpiece as would be performed by hand lapping, whereby the workpiece holder with affixed workpiece is linearly translated in a repetitive, reciprocal manner across the lapping plate while also intermittently rotated about its own axis in small angular increments, to ensure uniform lapping of the workpiece. The advantages provided by the mechanical movements of the workpiece emulating the workpiece movements of hand lapping, include a very uniform coverage and attendant uniform wear of the stainless steel or nickel lapping plate, from having the workpiece traverse the entire diametric length of the stainless steel or nickel lapping plate with each linear stroke of movement. The large stainless steel or nickel lapping plate therefore does not have to be rotated continuously since the sole purpose for its rotation is to ensure uniform wear across the surface, rather than for the abrading or removal of material from the workpiece which is accomplished rather, primarily through the linear, reciprocal movement of the workpiece.
Although other automated apparatus designs and methods exist for lapping and/or polishing optical, semiconductor and optoelectronic materials, the alternative existing methods and automated apparatus do not offer the capability for simultaneously lapping and polishing the full range of optical, semiconductor and optoelectronic materials in a single linear, automated apparatus using clean, high purity water based abrasive slurry with a corrosion resistant stainless steel or nickel lapping plate supporting an affixed polishing pad of woven nylon or rayon material. Other methods and automated apparatus implement the lapping action using the more conventional, continuous rotational movement of the lapping plate beneath the workpiece which is positioned at the edge of the lapping plate, resulting in a non-uniform wear of the lapping plate, while in the present invention, a highly stable linear, reciprocal motion of the workpiece diametrically across the lapping plate with only intermittent rotation of the stainless steel or nickel lapping plate, ensures uniform Wear of the plate and obviates the need for periodic conditioning or reflattening of the lapping plate.
As illustrated in U.S. patent application Ser. No. 10/599,562, the method and apparatus proposed for polishing a workpiece relies on linear abrasive finishing rather than rotary abrasive finishing. A pair of adjacent parallel flat surface plates move linearly in opposite directions and the workpiece is pressed onto both of the plates and the workpiece is subjected to abrasive finishing by the relative movement between the rotation of the workpiece and the linear movement of the pair of surface plates. Belt polishers passing over a workpiece support may be used instead of the surface plates. The described invention for a linearly advancing polishing method and apparatus however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed circular workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
As illustrated in U.S. Pat. No. 5,487,697, the method and apparatus proposed for polishing a workpiece relies on using a rotary work holder travelling down a rail for polishing a workpiece with linear pads. The polishing pads have a long linear dimension relative to their width with uniform cross-section along the linear dimension and the wafer holder travels in a straight line parallel to the long linear dimension of the polishing pads. The described invention for a linear polishing method and apparatus however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
As illustrated in U.S. Pat. No. 5,749,769, the apparatus for a lapping process using microadvancement is described for optimizing the flatness of a magnetic head air bearing surface. The lapping machine includes a lapping plate having a grinding surface, a linear motion for moving the air bearing surface over the grinding surface in a first linear direction and a micro-advance mechanism for controllably advancing the workpiece over the grinding surface in a second direction that is perpendicular simultaneously, to provide a highly polished air bearing surface. The described invention for a linear polishing method and apparatus however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
As illustrated in U.S. Pat. No. 6,908,368, the method for implementing an advanced bi-directional linear polishing system is described where the chemical mechanical apparatus uses a portion of a polishing pad that is disposed under tension between a supply spool and a receive spool, with a motor providing the tension to either the supply spool or the receive spool and the other spool being locked during processing while the motor also advances the polishing pad if needed. A feedback mechanism ensures that consistent tension of the polishing pad is maintained. The described invention for a linear polishing method and apparatus however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
As illustrated in U.S. patent application Ser. No. 10/134,821, the method for implementing a linear polishing apparatus is described for improving the substrate uniformity. The linear polishing apparatus intended for polishing a semiconductor substrate has a polishing belt arrangement with at least two polishing belts forming a continuous loop with each belt having an outside polishing surface and smooth inside surface and are mounted side by side sharing a common axis at each end. A platen interposes each belt and is placed between the rollers, providing a polishing plane having a plurality of holes for compressed gas to impart an upward pressure against the polishing belts. The described invention for a linear polishing method and apparatus however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
As illustrated in U.S. patent application Ser. No. 09/820,107, the method for implementing a linear chemical polishing apparatus equipped with programmable pneumatic support platten is described which allows for controlling the polishing profile on a wafer surface during a linear CMP process. The programmable pneumatic platen is positioned juxtaposed to the bottom of a continuous belt for the linear CMP apparatus and positioned corresponding to the wafer carrier to force the polishing pad against the wafer surface to be polished using a plurality of holes for gas pressure to be applied in a predetermined pattern to the polishing pad in contact with the wafer. The described invention for a linear polishing method and apparatus however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
As illustrated in U.S. Pat. No. 6,462,409, the method for implementing a semiconductor wafer polishing apparatus is presented whereby a robotic handling system moves the semiconductor wafer between a belt module and a rotary module for respective linear and rotary polishing. A buff module and cleaning module are also provided in the system housing for buffing and cleaning the semiconductor wafer. The described invention for a semiconductor wafer polishing apparatus however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
As illustrated in U.S. Pat. No. 6,589,105, a method and system for pad tensioning in a bidirectional linear polisher is presented. The chemical mechanical polisher apparatus and method uses a section of a polishing pad kept disposed under tension between supply and receive spools with a motor providing the tension to either spool and the other being locked. If a new pad section is needed, the same motor providing the tension will advance the polishing pad a determined amount. The described invention for a bi-directional linear polishing apparatus however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
As illustrated in U.S. Pat. No. 6,179,695, a method and apparatus for chemical mechanical polishing is presented capable of polishing a surface very precisely at a high speed irrespective of the presence of a local defect on the surface to be polished using a multiplex ring-shaped polishing pad that effectively increases the surface to be polished and very precise and uniform polishing can be performed at high speed. Using a plurality of polishing pads, having different diameters smaller than the diameter of the surface to be polished, provided with an interval on the same revolution radius on a revolution table, very precise and uniform polishing is achieved. The described invention for a chemical mechanical polishing method and apparatus however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
As illustrated in U.S. Pat. No. 6,612,904, a field controlled polishing apparatus is presented, which includes a polishing pad, a bladder, a fluid and a flux guide where the bladder containing fluid supports the polishing pad positioned adjacent to the surface to be polished. Flux guides positioned along a portion of the bladder, direct a field or a magnetic flux to selected locations of the bladder. The method of polishing a surface adjusts the field or the magnetic flux emanating from the flux guides which changes the mechanical properties of the fluid and by adjusting the magnitude of the field or magnetic flux flowing from the guides, independent pressure adjustments occur at selected locations of the bladder that control the polishing profile of the surface. The described field controlled polishing apparatus invention however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
As illustrated in U.S. patent application Ser. No. 09/893,625, a polishing apparatus is presented for polishing a workpiece such as a semiconductor wafer and allows the polishing pad to be automatically replaced without stopping rotary or circulatory motion of a polishing table, which comprises a polishing table for rotary motion, a top ring above the polishing table for holding the workpiece to be polished, a pair of rolls rotatable about their own axes, movable in unison with the polishing table and a polishing pad which is wound on one of the rolls and supplied over an upper surface of the polishing table toward the other of the rolls. The described polishing apparatus invention however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
As illustrated in U.S. Pat. No. 4,993,190, a polishing apparatus invention is presented for polishing optical components and mechanical parts requiring a high surface precision, such as lenses and mirrors by pressing a running tape to such components. The described polishing apparatus invention however, does not propose a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming conditioning or reflattening of the lapping plate.
Note that the above methods and apparatus for automated lapping and polishing of optical components, semiconductor and optoelectronic materials do not envision, nor describe a linear, automated apparatus and method for clean, high purity, simultaneous lapping and polishing of optics, semiconductors and optoelectronic materials using a circular, corrosion resistant stainless steel or nickel lapping plate with affixed circular synthetic nylon or rayon pad that allows clean, high purity water based abrasives to be utilized, whereby material is abraded from the workpiece primarily through the linear, reciprocal back and forth movement of the workpiece holder diametrically across the circular lapping plate, with intermittent rotation in step increments of the workpiece holder and affixed workpiece, tracing arcs of 180 degrees, first in a clockwise and subsequently counterclockwise direction, and with further intermittent rotation of the circular lapping plate, the latter for the sole purpose of ensuring a uniform wear on the circular nylon or rayon pad and lapping plate that fully eliminates the need for periodic, time consuming, labor intensive conditioning or reflattening of the lapping plate.